1. Field of the Invention
The present invention relates to an optical connection system for the bidirectional exchange of data between a central unit and peripheral units, and in particular peripheral units integral with a frame driven with a rotary movement.
2. Background of the Invention
The system of the invention applies more particularly to certain radar antennae of the electronic sweep type. For this type of antenna, there is associated with the mechanical rotation of the aerial an electronic deflection of the beam, in a cone having an axis perpendicular to the plane of the aerial and passing through its center. The electronic deflection is obtained by controlling the phase state of phase shift modules situated on the front face of the plane of the antenna. The order of size of the number of phase shift modules is about a thousand.
The phase of each pase shift module is computed, then displayed by an assembly of computing circuits situated on the rotary part of the antenna. The input data is elaborated by a central computer of the radar situated in the fixed part thereof. It is then necessary to transmit this information to the rotary part and to receive in return control information from the phase shift modules. These exchanges take place, according to the prior art, by means of a rotary joint comprising a ring collector and by means of electric connections. This ring collector is heavy and cumbersome because, besides rings intended for transmitting information signals, it contains power rings. Furthermore, numerous precautions must be taken to ensure the reliability of the transmissions:
contact by several brushes;
protection against oxidization so as to avoid contact defects if the antenna does not rotate for a period of time;
judicious distribution of the signal rings and the power rings on the collector, so as not to exceed the maximum common mode level of the line transmitters and receives used in the electric connections and, in the case of mechanical failure, so as to avoid the possibility of direct contact between the power rings and the wires conveying the information signals;
arrangments made for a good quality ground return.
All these precautions result, among other things, in limiting the possible flow of information exchange. The transmission rates are typically limited to 1 Mbit/s, the transmissions generally taking place by exchange of signals of the pulse type. This leads to splitting the communication paths into two :an "ascending" unidirectional path for the central computerperipheral unit connection and a "descending" unidirectional path for the reverse connection.